1. Field of the Invention
The present invention relates to a zoom optical system and an imaging apparatus using the zoom optical system.
2. Description of the Related Art
Requirement for compact and thin design of electronic imaging apparatuses has been more and more urgent in recent years. To meet the requirement, it is very important to shorten the total length of optical systems used in imaging apparatuses, such as a photographing optical system, a finder optical system, etc.
Regarding such an optical system, there is a limit to shorten the total length by reducing the number of constituent elements. Therefore, compact and thin design of the optical system in its entirety is aimed at by folding the optical system using mirrors. Furthermore, in folding the optical system, a space for a portion of folding is required. In addition, having a variator group that has a magnification varying function, a compensator group that compensates for a shift of an image surface caused by the magnification change and for aberrations, a focusing group that performs focusing on an object, etc, a zoom optical system is configured to perform magnification change and focusing by shifting, of these len's groups, predetermined lens groups along the optical axis, and thus a space for the movement of the lens groups is needed.
As an optical system thus configured, for example, each of Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 8-248318 and Japanese Patent Application Preliminary Publication (KOKAI) No. Hei 11-220646 discloses an imaging apparatus using a zoom optical system that is given a compact size with the path of rays being folded back.
In such a zoom optical system, in magnification change or focusing, a motor is driven to move lenses.